ESI–MS/MS and MALDI-IMS Localization Reveal Alterations in Phosphatidic Acid, Diacylglycerol, and DHA in Glioma Stem Cell Xenografts

Abstract

Glioblastoma (GBM) is the most common adult primary brain tumor. Despite aggressive multimodal therapy, the survival of patients with GBM remains dismal. However, recent evidence has demonstrated the promise of bone marrow-derived mesenchymal stem cells (BM-hMSCs) as a therapeutic delivery vehicle for anti-glioma agents, due to their ability to migrate or home to human gliomas. While several studies have demonstrated the feasibility of harnessing the homing capacity of BM-hMSCs for targeted delivery of cancer therapeutics, it is now also evident, based on clinically relevant glioma stem cell (GSC) models of GBMs, that BM-hMSCs demonstrate variable tropism towards these tumors. In this study, we compared the lipid environment of GSC xenografts that attract BM-hMSCs (N=9) with those that do not attract (N=9), to identify lipid modalities that are conducive to homing of BM-hMSC to GBMs. We identified lipids directly from tissue by matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) and electrospray ionization-tandem mass spectrometry (ESI-MS/MS) of lipid extracts. Several species of signaling lipids, including phosphatidic acid (PA 36:2, PA 40:5, PA 42:5, and PA 42:7) and diacylglycerol (DAG 34:0, DAG 34:1, DAG 36:1, DAG 38:4, DAG 38:6, and DAG 40:6) were lower in attracting xenografts. Molecular lipid images showed that PA (36:2), DAG (40:6), and docosahexaenoic acid (DHA) were decreased within tumor regions of attracting xenografts. Our results provide the first evidence for lipid signaling pathways and lipid-mediated tumor inflammatory responses in the homing of BM-hMSCs to GSC xenografts. Our studies provide new fundamental knowledge on the molecular correlates of the differential homing capacity of BM-hMSCs toward GSC xenografts.

Quantitative proteomics and transcriptomics reveals metabolic differences in attracting and non-attracting human-in-mouse glioma stem cell xenografts and stromal cells

“…The predicted outcome of this would be a decrease in the biosynthesis of DHA in attractors, which supports our previous lipidomic study [59]. We also show an overall down-regulation in glucose-dependent metabolic pathways -glycolysis and the PPPin attractors relative to non-attractors.…”

“…Our lab has previously shown, using ESI-MS/MS and MALDI-IMS followed by MALDI-MS/MS, that DHA, the precursor to inflammatory-resolving molecules, is decreased in the attractor phenotype [59]. The fact that the proteomic data from our xenografts is congruent with our previous lipidomic analysis on these samples adds a level of confidence to our dataset, providing orthogonal validation to the lower expression levels of the DHA observed in attractors.…”

“…The fact that the proteomic data from our xenografts is congruent with our previous lipidomic analysis on these samples adds a level of confidence to our dataset, providing orthogonal validation to the lower expression levels of the DHA observed in attractors. The decreased levels of DHA and the proteins responsible for its synthesis may be a key component to the homing permissive environment of attractors [59].…”

Integrated Transcriptomic and Glycomic Profiling of Glioma Stem Cell Xenografts

“…Anderson Cancer Center (MDACC, Houston, TX) as previously described 20, 21 . All animal procedures were undertaken within the guidelines prescribed by the MDACC Animal Care and Use Committee, the USDA Animal Welfare Act, and the Guide for the Care and Use of Laboratory Animals (NIH).…”

“…Animals were anesthetized by intraperitoneal injection of ketamine/xylazine and sacrificed as previously described 20 . Brains were removed immediately and flash frozen in liquid nitrogen vapor 28 and sliced 1.5 mm thick using a brain matrix.…”